1. Field of the Invention
The present invention relates to an ink, a production method of the ink, the materials for producing the ink and the printed matter wherein printing is made by use of the ink.
2. Description of the Related Art
It has so far been well known that aluminum flake is added to an ink to prepare a metallic tone ink. However, a printed matter printed with such a metallic tone ink has minute glittering dots, but does not exhibit any specular gloss.
Thereafter, the use of an ink, in which a special aluminum powder is utilized and the amounts of a binding agent and a diluting solvent are specified, has lead to the advent of a technique with which a bright printed matter with metallic luster can be obtained (see Patent Document 1). However, in practice, it has been found that no printed matter high in specular gloss can be obtained even when printing is made with the ink described in Patent Document 1.
In these circumstances, an ink has been proposed which comprises 100 parts by weight of an aluminum flake containing aluminum flakes of 0.5 μm or less in thickness and 20 μm2 to 2,000 μm2 in flake area in a content of 75% or more, 15 to 200 parts by weight of abinder polymer, and 600 to 3,000 parts by weight of a solvent (Patent Document 2). It is true that following the description of Patent Document 2, a printed matter higher in specular gloss than a printed matter described in Patent Document 1 can be obtained.
However, the types of solvents, utilized in an ink which imparts to a printed matter metallic luster or specular gloss, are at best described in paragraph [0012] in Patent Document 2 as such that “Additionally, the solvent utilized is the one that dissolves the above described binder polymer and dilutes the solution thus obtained, and the general examples of such a solvent include esters, ethers, ketones, aromatic hydrocarbons and the like.” Additionally, even in the examples concerned, ketone based solvents and glycol ether based solvents are merely exemplified, but the compound names of such solvents are not specified.
Additionally, in Patent Document 1, particularly in paragraph [0024], there is found a description that “Furthermore, as the diluting solvent utilized in the present invention, any solvent capable of dissolving and diluting a binding agent used can be optionally utilized, and hence the solvent can be selected according to the printing method involved in such a way that the solvent is optionally selected from the commonly used solvents including alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; ktones such as acetone, isophorone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve and ethyl cellosolve; and aromatic hydrocarbons such as toluene and xylene; additionally, aliphatic hydrocarbons, ethers and the like, commonly used as diluents and compatible with the above described solvents but incapable of dissolving the binding agents, can also be used as printing aids and dryness regulators.” Furthermore, in paragraph [0039] in Patent Document 1, although the standard for solvent selection is not presented, there is found a description that “Incidentally, the adaptabilities of the bright ink 2 with respect to various types of substrates have been examined, and the results obtained are as shown in Table 5,” and there is found another description in Table 5 that isopropyl alcohol and cellosolves are adaptable to various resins such as polyvinyl chloride, PET (polyester), acrylic resin, and polycarbonate. However, no description is found as to how isopropyl alcohol and cellosolves adapt.
[Patent Document 1]
Japanese Patent No. 2784566
[Patent Document 2]
Japanese patent No. 3151606
When printing is made according to Patent Document 1 and Patent Document 2, a bright printed matter or a specular surface printed matter can be obtained, but it has been found that serious drawbacks are generated when such printing is applied to industrial mass production, particularly, when the screen printing is applied to mass printing.
As a first drawback, the inks described in Patent Document 1 and Patent Document 2 each contains a large content of solvent, and hence mass printing is not preferable because the working environment is remarkably degraded in operation with ordinary facilities when a highly toxic solvent is used for which the LD 50 value representing the mouse oral toxicity is 2,000 mg/kg or less, particularly, 1,600 mg/kg or less, or a solvent is used for which the vapor pressure is high (drawback <1>). As a second drawback, in making mass printing, the specular gloss appearance is degraded and printing unevenness is generated with increasing number of the printed sheets when the number of the printed sheets is large (drawback <2>). As a third drawback, when printing is made on the backside of a transparent polycarbonate substrate and viewing is made from the front surface side of the substrate, the specular gloss appearance is sometimes remarkably degraded (drawback <3>).
Accordingly, an object of the present invention is the provision of an ink to meet the purpose of concurrently resolving the above described drawback <1>, drawback <2>, and drawback <3>, a production method of the ink, the materials for producing the ink, and the printed matter wherein printing is made by use of the ink.